The worst U.S. cities and states for particulate pollution

Updated on April 15, 2024
Written by
Amparo Lopez
Amparo is a staff writer for HouseFresh, having joined us in 2023. She is a sustainability advocate, holding degrees in communications, human-centered design and environmental policy. Her work has a focus on air pollution and climate change.

Our verdict

Despite levels of PM2.5 and PM10 gradually decreasing in recent years, according to the EPA, the issue of particulate pollution continues to be of grave concern.

In analyzing states and cities, we found that, in general, western areas showed the worst results for PM10 and PM2.5, with the arid, hot states of California and Nevada revealing the highest levels. According to the American Lung Association, climate change has led to record-high temperatures and surges in particulate pollution can be directly related to heat.

Eastern states such as New Jersey and New York may be seeing improved scores in part due to the success of the Clean Air Act. While this has successfully resulted in lower emissions, it’s clear that all states and cities must continue to work at reducing particulate pollution for the overall health of the nation.

Breathing clean, healthy air is a universal human right. Unfortunately, many people in the United States are being exposed to dangerous levels of contaminated air, which can have short- and long-term consequences.

According to the EPA, particulate matter (PM2.5 and PM10) is one of the significant sources of harmful air pollution, and the ultrafine, inhalable PM2.5 particles are especially hazardous to health; we wanted to determine which U.S. states and cities are the worst (and best) for particulate pollution. 

Our detailed breakdown of the highest levels of PM2.5 and PM10 will tell you just how much the place you work or live in can affect your health.

There are over 2,000 ambient outdoor air monitors throughout the United States. These monitors measure the concentrations of some of the most harmful pollutants, including inhalable particulate matter, toxic gasses and ozone.

To determine the states with the worst air quality, we ranked states based on Particulate data from the Air Quality Index (AQI).

Using data from the U.S. Environmental Protection Agency, we aggregated the latest data on annual AQI from the county to the state level. For city data, we crosswalked county-level data with county seat assignments.

Key findings 

  • The western state of Nevada is the worst in the U.S. for both PM10 (180 μg/m3) and PM2.5 (11.875 μg/m3). According to the American Lung Association, weather patterns such as heat and drought are major contributing factors, as are the frequency of wildfires. 
  • The Mid-Atlantic region of Maryland is the best state for PM10, with 23.667 μg/m3.
  • Hawaii was the best state for PM2.5 — just 3.5 μg/m3. While climate change and volcanic activity are a continuing threat, according to the World Population Review. It should be mentioned that this data was collected before the recent wildfire swept across Maui, which would’ve seen a momentary spike in PM2.5. 
  • The worst cities for PM10 and PM2.5 concentrations are in hot, western states, such as California, Arizona and Nevada. California towns are the worst, with Visalia number one for PM2.5 (21 μg/m3) and Bridgeport for PM10 (1,230 μg/m3). Vehicle emissions, wildfires and heatwaves are among the most significant sources, according to
  • East Coast cities such as Jersey City and Queens rank much better for PM2.5 with 13 μg/m3.  

What are PM2.5 and PM10?

PM means particulate matter (or particle pollution). It’s a mixture of tiny liquid droplets and solid particles in the air, such as dust, dirt and smoke. It can be found indoors — for example, via cooking — and outdoors, where the most common sources are vehicle exhausts, power plants and forest fires.

Some particles are visible to the naked eye, while others can only be seen under a microscope. To distinguish and categorize the various particles, size measurements are used. 

The larger particulate matter is PM10 (10 microns/micrometers or smaller in diameter), while the smaller particulate matter is PM2.5 (2.5 microns or smaller).

If you’re unsure how small 2.5 is, consider that a human hair is approximately 70 microns in diameter. And these minuscule particles are the most harmful to your health precisely because they are so tiny. According to the EPA, this is because they can penetrate your lungs and even enter your bloodstream. Studies have shown that PM2.5 can even pass directly through to the brain through the olfactory nerve.

Short-term health effects can include:

  • Difficulty breathing
  • Eye, nose and throat irritation
  • Lung irritation
  • Coughing
  • Sneezing.

However, various studies highlight the long-term health implications of PM exposure, including an increased risk of heart disease. Certain groups of people are also more at risk of particulate pollution. For example, older adults, babies, young children and individuals with underlying heart or lung conditions, such as asthma.

The worst U.S. Cities for PM2.5 pollution? California is home to 10 of them

Let’s kick things off by turning our attention now to cities. California has ten entries out of the worst 20 cities for PM2.5 and Visalia is the worst for PM2.5 (21 μg/m3). 

Los Angeles and Bakersfield are also in the top 20, with scores of 13.4 μg/m3 and 20 μg/m3, respectively. As California is the most populous U.S. state, this has most likely increased vehicle emissions. Moreover, frequent sunny days and low rainfall can exacerbate particulate pollution.

The East Coast ranks as a better place for PM2.5. According to the American Lung Association’s “State of the Air” report, there’s a widening gap between eastern and western cities, with historically urban states like New Jersey now seeing better grades, partly due to policy-driven emission reductions.  

It is worth mentioning that ten out of the 20 worst cities for PM10 are found in The Golden State’’ of California. Bridgeport overwhelmingly shows the highest levels with 1,230 μg/m3. 

To put that into perspective, the second worst city is Wheatland, Wyoming, with half that amount – 559 μg/m3. As Bridgeport is located in a valley, this could suggest why its score is so high: surrounding mountain ranges trap air pollutants.

Conversely, although a member of the Sun Belt states like California, the flat topography of Deming in New Mexico has considerably lower levels of PM10 with 193 μg/m3.

Nevada is the worst U.S. state for PM2.5 (and PM10) pollution

Our map shows PM2.5 levels across the U.S., but there are some correlations with PM10. 

Nevada is the worst state for both types of particulate pollution. With extreme heat, wildfires and droughts, Las Vegas, in particular, experienced “unhealthy spikes in particle pollution,” according to the American Lung Association’s 2023 “State of the Air” report. Neighboring state California, meanwhile, is ranked third worst for both PM2.5 and PM10. 

Hawaii, regarded as having the cleanest air throughout the U.S., is the best for PM2.5, with a score of just 3.5 μg/m3. 

And Maryland is best for PM10 (23.667 μg/m3). The state’s Healthy Air Act may partly suggest why — the Act has the most rigorous power plant emission laws on the East Coast. 

Top 10 worst U.S. states for PM2.5 pollution

Now, let’s explore the worst states for PM2.5 in more detail, looking closely at the possible reasons for each state’s poor air quality. 

#1. Nevada (PM2.5 levels: 11.875 μg/m3)

Image Source: Pahrump Valley Times / 2021, Richard Stephens

Nevada faces frequent wildfires each year due to dry conditions, abundant dry fuels and invasive plants like cheatgrass. This makes the state highly vulnerable to dangerous fire seasons in summer and fall. 

Mountainous areas such as Reno experience peaks in air pollution caused by wildfire smoke, while Southern Nevada experiences hazy skies and higher particle pollution levels from wildfires in distant locations.

Nevada also experiences temperature inversions during winter when cold air gets capped under warmer air. This traps pollution near the ground, preventing it from dispersing into the atmosphere. As a result, the air Nevadans breathe is impacted by concentrated pollution at ground level.


When preparing for a wildfire evacuation, the University of Nevada, Reno, has provided five helpful tips:

1. Cotton or wool clothes, including long pants and a long-sleeved shirt or jacket. Remember to protect your head with a hat and your feet with sturdy boots.

2. Carry gloves, water for hydration and goggles to shield your eyes.

3. Keep your cell phone, a flashlight and a portable radio handy for communication and staying informed at all times.

4. Stay tuned to a local radio station for instructions and updates.

5. Consider using a NIOSH N95 or P100 mask

If you’re staying indoors and not evacuating, running your air purifier round-the-clock for optimal indoor air quality is ideal. Find out why running your air purifier continuously is a smart choice for improving your home’s air quality here

#2. Oregon (PM2.5 levels: 11.286 μg/m3)

Image Source: NRDC / 2019, Oregon Department of Forestry

​​Due to its vast size, air quality conditions in Oregon vary across the state. However, it has witnessed an overall increase in bad air days primarily attributed to wildfire smoke. The Pacific Northwest region continues grappling with the impacts of climate change, the subsequent extreme drought conditions and prolonged wildfire seasons.

During winter, Oregon also experiences a rise in particulate matter levels due to residential wood burning for heating. As the population grows, emissions from traffic, construction and wood stoves also increase. Plus, winter cool air inversions trap pollution emissions in the valleys, leading to PM2.5 accumulation in the air.

💡 Pro Tips:

1. Avoid using woodstoves in winter, especially on bad air days. Instead, try to use a different heat source whenever possible. If a woodstove is your only option, the Oregon Department of Environmental Quality (DEQ) offers a Woodstove program to help replace woodburning heaters.

2. When the DEQ issues an advisory for wildfire smoke, stay indoors as much as possible, drink plenty of water and avoid other sources of indoor smoke like burning cigarettes, candles and wood-burning furnaces.
👓 Read More: During wildfires, using an air purifier designed for wildfire smoke can help remove particulate pollution caused by the smoke, improving indoor air quality.

#3. California (PM2.5 levels: 10.938 μg/m3)

Image Source: BBC / 2018

The American Lung Association’s State of the Air report analyses short-term and year-round particulate pollution trends throughout the U.S. In their latest report, Californian cities such as Bakersfield, Visalia and the Fresno-Madera-Hanford area lead both lists with some of the highest air pollution levels.

The state is known for its wildfire seasons, usually between late summer and early autumn. Climate change has intensified droughts and increased temperatures in the past two decades, resulting in more intense, destructive and longer wildfires. With many cities nestled within valleys, air pollution gets trapped by the mountains retaining particle pollution for longer periods. 

Unfortunately, wildfires are not the only source of particulate matter. Cities with high power plant emissions and local industrial and mobile sources, such as Los Angeles, which has five airports and historically high levels of traffic, are also affected by PM2.5 concentrations.

💡 Pro Tip: Wildfire smoke can be hazardous. The best way to deal with it is by staying indoors and keeping your doors and windows closed. Take it easy on bad air days and keep your activity levels low. Keep track of the air quality with BreatheWell or AirNow.
👓 Read More: Particle pollution can quickly get indoors, and an air purifier can become really handy during wildfire seasons. If you’re curious about the benefits of air purifiers and how they can enhance indoor air quality, discover how they work and all the advantages they offer here

#4. Kansas (PM2.5 levels: 10.5 μg/m3)

Image Source: KCUR / 2021, Charlie Riedel

Kansas faces significant levels of PM2.5 pollution from multiple sources. The state’s thriving agricultural and industrial sectors, including petroleum refineries and grain processing or storage facilities, contribute to accumulated particulate matter in the air. Vehicle emissions from cars, trucks and buses, lawnmowers and tractors used in agricultural activities are also significant sources.

Environmental factors play a role, too, as Kansas frequently faces droughts that result in dry fuels, low humidity and gusty winds. These conditions increase the risk of dangerous wildfires in the region. 

💡 Pro Tip: Stay informed about the air quality daily. The Kansas Department of Health and Environment (KDHE) offers real-time monitoring data through the Kansas Air Quality Monitoring Network. 

This data provides information about the levels of the five primary pollutants: carbon monoxide, ozone, nitrogen oxides, particulate matter and sulfur dioxide.
👓 Read More: Air purifiers are highly effective in improving indoor air quality, especially when dealing with high levels of outdoor PM2.5 pollution. To maximize the benefits of your air purifier, here are some helpful tips to consider.

#5. Oklahoma (PM2.5 levels: 10.45 μg/m3)

Image Source: KGOU / 2019, Woodward News

Like many other western states, Oklahoma is no stranger to the devastating impact of droughts and subsequent wildfires. In 2022 and 2023, the drought conditions reached exceptional levels, as confirmed by the National Integrated Drought Information System (NIDIS), leading to widespread wildfires.

However, higher concentrations of PM2.5 pollution are typically found in major cities such as Oklahoma City and Tulsa. These urban areas serve as hotspots for various industrial activities, including aerospace, energy, health care, technology, manufacturing and transportation. 

As a result, the air becomes burdened with higher levels of pollution stemming from industrial emissions and the exhaust fumes of vehicles that crowd the roads.

💡 Pro Tip: Stay informed during air quality alerts in Oklahoma by signing up for text and email notifications from the Oklahoma Department of Environmental Quality. Be prepared and take necessary measures with timely Air Quality Health Advisories.
👓 Read More: Air purifiers equipped with HEPA filters effectively reduce harmful airborne pollutants and contaminants from indoor air. These filters can capture particles as small as 0.3 microns in size. Discover more about the functionality of HEPA filters and how they work by exploring further information here.

#6. Idaho (PM2.5 levels: 9.7 μg/m3)

Image Source: NYTimes / 2009, Greg Kreller

Idaho grapples with high levels of PM2.5 and wildfires are a major source. Like many other western states, Idaho has witnessed an alarming increase in the frequency and intensity of wildfires in recent years, mainly due to climate change and poor forest management practices. 

Furthermore, the state’s rapidly growing population adds to the PM2.5 levels in the air. Residential wood burning sees a rise during winter and vehicle emissions increase year-round. Besides the cars on the road, other sources like agricultural equipment, trains and planes also generate particulate pollution. 

Compounding the issue is Idaho’s unique geography, with numerous cities nestled in valleys or close to mountains that hinder the dispersion of fine particulate matter.

💡 Pro Tips:

1. If the air quality in your area is poor, try to limit your time outdoors. While staying home may not be possible for everyone, if you must be outside during unhealthy air conditions, it is strongly advised to wear an N95 mask. 

2. Stay updated on the air quality in Idaho through the Department of Environmental Quality Real-Time Map, hourly updated with the air quality data from over 30 monitoring stations across the state.
👓 Read More: Check out our top recommendations to protect your home from wildfire smoke, with tips to create a safe indoor environment when the air gets smoky.

#7. Georgia (PM2.5 levels: 9.55 μg/m3)

Image Source: Georgia Today / 2023,  Shermazana

The Georgia Department of Natural Resources monitors fifty-three different particulate matter species. According to their 2021 Ambient Monitoring Report, the highest concentrations were observed in sulfate and organic carbon particulates, both associated with fossil fuels, wood burning and materials containing sulfur.

One of the primary sources of PM2.5 in Georgia is vehicle emissions, including large trucks and lorries used for transportation and personal vehicles. Power plants and factories, many of which rely on diesel fuel, natural gas, or coal for energy production, also add to the pollution levels across the state. 

Open agricultural burning — commonly practiced in Georgia for dealing with agricultural waste— and forest and prescribed fires further contribute to the presence of PM2.5 particles.

💡 Pro Tip: Opt for carpooling, vanpooling and biking.The Atlanta Regional Commission’s Georgia Commute Options program offers alternative transportation solutions for metro Atlanta and surrounding areas.
👓 Read More: PM2.5 can easily get into your home. But air purifiers can make a huge difference and improve your home air quality. That’s why we compiled the best air purifiers in 2023.

#8. Illinois (PM2.5 levels: 9.506 μg/m3)

Image Source: Chicago Tribune / 2020, Antonio Perez

Exposure to PM2.5 in Illinois varies greatly. Urban areas and downwind regions have the highest concentrations. Chicago is the most affected and ranked 23rd among the most-polluted cities in the U.S. for annual particle pollution, as reported by the American Lung Association’s 2023 State of The Air report.

In urban areas, pollution primarily originates from vehicles such as cars, heavy-duty trucks and buses. Cook County, for example, serves as a significant national hub for freight transportation, with considerable industrial activity concentrated along major highways.

💡 Pro Tip: To minimize the entry of outdoor particle matter into your home, close windows and doors when the outdoor particle levels are high. Stay updated on the air quality levels in your city at AirNow.
👓 Read More: Besides high PM2.5 concentrations, Illinois also faces elevated ozone levels. Therefore, when selecting an air purifier to keep your indoor air fresh, we recommend an ozone-free air purifier.

#9. Indiana (PM2.5 levels: 9.267 μg/m3)

Image Source: Indiana Public Radio / 2018, Pixnio

Like many other states, Indiana deals with high PM2.5 pollution caused by burning fossil fuels, especially in urban areas. The recent State of the Air report of the American Lung Association ranked the Indianapolis metro area as the 13th most polluted for year-round particle pollution, the same as last year.

In Indiana, most people rely heavily on their cars, which has led to a poor and underused public transportation system. A robust transportation sector with heavy-duty trucks and other gas-powered machines —like lawnmowers— increase the already high amount of burned fossil fuels. 

Southwest in the state, coal-fired power plants release PM2.5 emissions that disperse across Indiana and beyond due to air currents.

💡 Pro Tip: Living near highways makes you more likely to be exposed to regular particulate matter pollution. To reduce indoor pollution when PM2.5 levels are high, avoid burning anything inside (wood fireplaces, gas logs, candles, incense), don’t smoke indoors and open windows for fresh air when the air quality is good.
👓 Read More: Here are our top-pick air purifiers for traffic pollution to improve indoor air quality during days with high particulate matter levels. 

#10. Kentucky (PM2.5 levels: 9.131 μg/m3)

Image Source: Courier Journal / 2023, Matt Stone

Kentucky’s energy needs heavily depend on coal, with coal-fired power plants supplying a significant 71% of the state’s electricity in 2021. The extraction method of mountaintop mining releases harmful pollutants, creating dust clouds that affect air quality. The latter transportation and burning of coal contribute to increased PM2.5 levels in the atmosphere.

Besides the coal-related pollution, Kentucky is affected by forest fires, especially during the fall and spring seasons. These thrive on the dry forest floor and low humidity, while the smoke plumes further add to the PM2.5 pollution in the state. 

The use of firewood in homes, especially during the colder winter months, also adds to the overall issue.

💡 Pro Tip: By improving your home’s energy efficiency, you can reduce your reliance on coal and wood burning in winter while also cutting down on heating expenses.
👓 Read More: If you are into efficiency, opt for an air purifier with washable filters to reduce waste and keep your indoor air clean, even on days with high PM2.5 levels outdoors.

Top 10 Worst U.S. States for PM10 Pollution

Now let’s see which states suffer from high levels of PM10. As you’ll see, many states rife with PM205 also suffer from PM10 pollution. 

#1. Nevada (PM10 levels: 180 μg/m3)

Image Source: West Coast Flying Adventures/ 2013, Matt Stone

Extreme heat and dry conditions in Nevada create the perfect conditions for intense dust storms, especially during prolonged periods of drought. These storms carry particulate matter called fugitive dust, also generated by various activities like construction and urban development. Fugitive dust includes particles from paved and unpaved roads, construction sites and disturbed vacant land.

In addition, the major population centers of Las Vegas Valley and the Reno-Sparks area experience heightened air pollution due to heavy vehicle usage. Emissions from vehicles on busy roads and near warehouses contribute to elevated levels of air pollution in these regions. 

Those residing close to these pollution sources face greater exposure to high concentrations of air pollutants.

💡 Pro Tip:  Look out for high wind warnings, they mean a dust storm is probably on its way. With wind speeds reaching 30-50mph or more, expect a significant amount of dust blowing around.
👓 Read More: During a dust storm, dust can find its way into your home even with your windows and doors tightly shut. If you’ve ever wondered about the origins of household dust and where it comes from, learn all about it here.

#2. New Mexico (PM10 levels: 174.667 μg/m3)

Image Source: Las Cruces Sun News / 2017, Josh Bachman

New Mexico’s arid climate, characterized by low precipitation and humidity, creates favorable conditions for dust storms. Strong winds whip up dust from dry, exposed soil, leading to PM10 pollution. Known as haboobs, these heavy winds are most common during the Summer Monsoon season between January and April.

In addition to dust storms, strong winds fuel wildfires — a natural occurrence in Southwest ecosystems — particularly during droughts and high temperatures.

Various industries also play a role in the state’s high levels of particulate matter. Oil drilling, dryland farming, cattle rearing and mineral extraction significantly impact New Mexico’s air quality.

💡 Pro Tip: When it comes to severe dust storms, the best precaution is to stay indoors and avoid venturing outside. If you really need to go out, minimize your time outdoors and avoid intense physical activities.
👓 Read More: To tackle the effects of dust at home, check out our selection of the best air purifiers for dust.

#3. California (PM10 levels: 158.878 μg/m3)

Image Source: Los AngelesTimes / 2020, Brian van der Brug

While wildfires certainly contribute to particle pollution in California, the Year-round Particle Pollution Trend analysis by the American Lung Association reveals that other sources also impact air quality in the state.

Intensive crop farming, coupled with heavy fertilization practices, promotes the formation of airborne particulate matter. Moreover, agricultural activities result in high levels of transportation pollution, primarily from heavy-duty trucks. 

In fact, California’s vehicle emissions, including cars, trucks and other vehicles, account for approximately 80% of the state’s overall air pollution. Given California’s high population, fireplaces and woodstoves also contribute considerably to PM10 pollution.

💡 Pro Tip: Consider retiring your older, high-polluting cars and replace them with zero or near-zero emission vehicles with the Clean Cars 4 All program.
👓 Read More: While transitioning to zero-emission vehicles is still in progress, car fumes can still affect indoor air quality.

#4. Arizona (PM10 levels: 143.455 μg/m3)

Image Source: Arizona State Department / 2020, ADOT

Arizona has a wide range of climates, from snowy forests in the north to arid conditions in the south. The southern region experiences massive dust storms called haboobs that sweep across the desert and farm fields, carrying dust particles and dry soils into the air. These strong winds occur regularly during the summer monsoon in Phoenix and Central Arizona.

During the winter holiday, the burning of wood in fire pits, fireplaces and fireworks release PM into the air. Additionally, these particulate matter levels can also rise with calmer weather conditions, contributing to year-round air pollution.

The state’s industrial activities also affect the air quality issue. The crushing and grinding of rocks and soil release particles into the atmosphere, while factories and transportation generate dirt and dust.

💡 Pro Tip: When the air quality forecast shows high levels of pollutants, there are simple steps you can take to reduce your exposure. 

1. Spend less time outdoors, especially when engaging in physical activities. 

2. Consider rescheduling outdoor plans.

3. Avoid busy roads as much as possible. 
👓 Read More: Check out how to remove dust in indoor air to keep your home dust-free even during monsoon season.

#5. Wyoming (PM10 levels: 132.571 μg/m3)

Image Source: Public News Service / 2016, Rabe/Pixabay

Wyoming is a major coal producer in the United States, accounting for 41.4% of the country’s total production in 2021, according to the Energy Information Administration (EIA). Other leading coal-producing states include West Virginia (13.6%) and Pennsylvania (7.4%). 

However, the environmental impact of coal-fired power plants is a significant concern. It goes beyond the emissions released from their stacks, as these plants generate coal ash as a byproduct during combustion.

Coal ash, also known as fly ash, contributes to increased concentrations of PM10 near coal-burning power plants. Combined with emissions from landfills and surface impoundments, it can lead to heightened levels of PM10 in communities near these power plants.

💡 Pro Tip: Air quality can fluctuate quickly; staying informed is important. Make it a habit to check the air quality index (AQI) before planning your day. If the air quality is poor, consider minimizing your time outdoors to reduce exposure.
👓 Read More: When dealing with high levels of PM10, it’s crucial to consider the air quality inside your home. You might be wondering if an air purifier is worth the investment. They are. If you want to know why, we made a list of all the good reasons why they aren’t a waste of money.

#6. Washington (PM10 levels: 121.5 μg/m3)

Image Source: Yakima Herald-Republic/ 2020, Amanda Ray

Smoke is the main source of Washington’s high levels of particulate pollution. Wildfires are the largest source of particle pollution in Washington and the wildfire season typically lasts from early July until September, when regular rain returns to the Northwest. 

During colder months, PM concentration rises due to higher levels of wood burning from stoves, fireplaces and other wood-burning devices used for heating purposes. With temperature inversions during the cold months, polluted air gets trapped near the ground and accumulates in the lower atmosphere.

💡 Pro Tip:If you’re considering purchasing a wood stove or other wood-burning device, it’s important to know Washington’s rules regarding their use and installation. You can find a list of certified wood stoves and wood-burning devices on their website.
👓 Read More: Exposure to smoke can negatively affect your health; it is best to eliminate it as soon as possible. There are a few simple steps you can follow to do so. You can find them here.

#7. Idaho (PM10 levels: 121 μg/m3)

Image Source: Idaho News / 2022

Besides the seasonal wildfires and smoke plums that spread particulate matter in Idaho’s air, agricultural residue-burning practices and prescribed fires also add up to the PM10 particle levels throughout the state.

On the other hand, the rapid growth in population results in higher emissions from both private cars and freight transportation, intensifying the release of particulate matter into the air. The fugitive dust from roads, tires and brakes contributes to the already high levels of particulate matter.

The state’s topography plays a role as well. Temperature inversions during cold months can trap pollutants near valley bottoms, worsening the air quality in the area. 

💡 Pro Tip: Idaho’s Department of Environmental Quality’s Woodstove Program offers sponsorship to replace older, more polluting stoves with cleaner-burning EPA-certified heaters to reduce particle pollution during winter. Find more about the program here.
👓 Read More: Air purifiers with HEPA filters can make quite a difference in your indoor air quality. However, they do need some maintenance. HEPA filters usually last about six to twelve months, and then they need to be replaced. Learn more about how long they last and how to extend their life here.

#8. South Dakota (PM10 levels: 99.889 μg/m3)

Image Source: South Dakota Searchlight / 2023, Makenzie Huber

Its unique topography and weather conditions consistently affect South Dakota’s air quality. Specifically, when strong winds arise after extended dry periods, particularly in colder months, they can strip away the top layer of soil and suspend fine dust particles in the air.

Due to its geography, the Black Hills area is prone to temperature inversions. This means that the bowl-like shape of the land and the surrounding mountain ridges can trap pollutants near the ground, building up in the air to unhealthy levels.

Additionally, South Dakota takes the lead in producing mica, gravel, crushed stone and other industrial mining activities. These operations directly emit particulate matter into the air, further contributing to the state’s air quality challenges.

💡 Pro Tip:  During high wind alerts, it is safest to seek shelter indoors. However, if you find yourself outside during a wind advisory, take cover next to buildings or under a shelter, avoid roadways and be cautious of flying debris. Strong winds can cause tree limbs to break and street signs to become loose.
👓 Read More: Consider improving indoor air quality while staying indoors. A HEPA filter air purifier can make a significant difference and protect you from harmful outdoor pollutants. To learn more, check out our article on the 6 Science-Backed Benefits Of Air Purifiers.

#9. Montana (PM10 levels: 92.8 μg/m3)

Image Source: Missoula Public Health, City-County Health Department / 2017, Shannon Edney

Montana’s air quality challenges stem from particulate matter concentrations generated by wildfires across the Northwest. The changing climate has led to hotter and drier summers, with fires becoming more frequent and the wildfire season prolonging. But the smoke doesn’t just originate within Montana’s borders and comes from surrounding states, even as far as California or Canada. 

Montana has also experienced significant population growth, making it one of the fastest-growing states in the U.S., according to the U.S. Census Bureau. This population increase affects urban areas and extends to rural regions, further exacerbating the risk of wildfires.

💡 Pro Tip: If you don’t have access to an air quality monitor, you can still get a rough estimate of the air quality based on visibility. 

Here’s a simple method to follow:

Choose pre-determined landmarks of known distances on a clear day. Stand away from the sun and look for targets at these known distances.

 Determine the limit of your visible range:

  • If you can’t see beyond five miles, it indicates Unhealthy Air.

  • If your visibility is limited to two miles, it suggests Very Unhealthy Air.

  • If you can only see up to one mile, it means Hazardous Air.
👓 Read More: Being prepared for wildfire season goes beyond outdoor precautions — it also involves ensuring clean indoor air. A HEPA filter air purifier is an effective way to reduce health risks during wildfire smoke. 

To make the most of your air purifier and keep it running smoothly, check out our comprehensive guide on air purifier repair.

#10. Minnesota (PM10 levels: 97.333 μg/m3)

Image Source: MPR News / 2023, Ben Hovland

Air pollution and particulate matter in Minnesota primarily come from wood smoke, vehicles and local businesses. According to the Minnesota Pollution Control Agency’s 2022 Residential Wood Combustion Survey, residential wood burning accounted for 55% of the state’s direct fine particle emissions. While many people use wood for home heating, recreational fires are also common.

Transportation is another primary source of air pollution in the state. Cars, trucks and trains collectively contribute to almost half of Minnesota’s high PM levels. Diesel engines, commonly found in construction and agricultural equipment, play a significant role in these emissions. 

Additionally, large industrial facilities like factories and power plants contribute to air pollution, accounting for 21% of the total emissions in Minnesota.

💡 Pro Tip: Planning a bonfire in Minnesota? Keep it cozy and compliant. 

The state fire code specifies that outdoor recreational fires and portable fireplaces should not exceed 3 feet in size.  If you’re going bigger, you’ll need a burn permit from the Minnesota Department of Natural Resources (DNR). 
👓 Read More: During the winter months, when heating is crucial, placing a HEPA air purifier in your room can greatly enhance your sleep quality and indoor air. Here are some tips for optimizing its placement to maximize pollutant reduction while you sleep!

4 Ways of Dealing With Particulate Pollution

When the air outside is filled with particle pollution, it’s time to cozy up indoors. But remember, maintaining good indoor air quality also means reducing PM levels inside your home. 

Here are four bonus tips to help you achieve cleaner air indoors:

  1. Keep your living space clean: vacuum regularly if you have a HEPA filter vacuum (and if you do, don’t forget to change the filter regularly). Otherwise, dust surfaces and mop floors using damp cloths to trap and remove dust particles. Regular vacuums will stir up particles already inside your home. 
  1. Use extractor fans while cooking: This will minimize the release of smoke, grease and other particles into the air, preventing PM buildup and keeping your kitchen environment healthier.
  1. Be mindful of smoke sources: Avoid using anything that burns, such as wood-burning stoves and heaters, fireplaces, candles and incense. Smoking inside should also be avoided, as it can linger in the air for hours and spread throughout your home. 
  1. Consider using air cleaners: HEPA air purifiers are highly effective in removing particulate matter, dust and other pollutants from the air. They can significantly improve indoor air quality and reduce your exposure to PM.

Final Thoughts

Particulate pollution can be found both inside and outside the home. Outdoor sources, such as transport emissions, weather patterns and forest fires, can have severe consequences for health, especially the ultrafine PM2.5 particles. The good news is that states and cities throughout the U.S. have made distinct progress in reducing particulate pollution and improving overall air quality.  

However, our findings show there is still a long way to go. Climate change and the widening disparity between eastern and western states are some ongoing threats. Yet knowing where the most problematic locations are and determining why helps ensure that breathing clean, healthy air will ultimately be accessible for all.


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About the author

Amparo Lopez

Amparo is a staff writer for HouseFresh, having joined us in 2023. She is a sustainability advocate, holding degrees in communications, human-centered design and environmental policy. Her work has a focus on air pollution and climate change.

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